Water cooled rotor for dynamoelectric machines

ABSTRACT

A water cooled rotor for large turbine generators in which the water passages are protected against corrosion by liners of stainless steel or other corrosion resistant material. In order to permit differential thermal expansion, the liner in the axial shaft bore includes a bellows of special design to absorb the expansion of the liner.

United States Patent 11 1 1111 3,740,595 Heller et-al. 1 June 19, 1973[54] WATER COOLED ROTOR FOR 2,736,825 2/1956 Hill 310/54 DYNAMOELECTRICMACHINES 3,243,616 3/1966 Tudge... 310/54 3,582,977 6/1971 Smith....310/54 Inventors: Paul Heller, Murrysvllle; 2,214,616 9/1940 Jenks310/53 Sui-Chun Ying; James E. Luzader,

both of Monroevinei all of Pa. FOREIGN PATENTS OR APPLICATIONS 1,146,91231969 G tB 't' 310 4 [73] Assignee: Westinghouse Electric Corporation,tea n am /5 ',plttsburgh Pa. Primary Examiner-R. Skudy [22} Filed: July28, 1971', A ttorney-A. T. Stratton and F. P. Lyle 21 Appl. No.: 166,684

[57] ABSTRACT [52] US. Cl. 310/54, 310/64 A water cooled rotor for largeturbine generators in [51] Int. Cl. H02k 9/00 which the Water Passagesare protect1 against com) 5 Field f Search n 310 52 53 54 53 sion byliners of stainless steel or other corrosion resis- 310/ 59 1 4 tantmaterial. In order to permit differential thermal expansion, the linerin the axial shaft bore includes a be]- 5 References Cited lows ofspecial design to absorb the expansion of the UNITED STATES PATENTS3,497,736 2/1970 Cuny 310/54 4 Claims, 2 Drawing Figures ,43 2? 9 29 i xJ 53 Q 50 k5 i 46 5| 1&- 45 I42 "49 49- 53 {I}? 1 47 2; 50 V 2? fPatented June 19, 1973 2 SheetbF-Sheet 1 Patented June 19, 19733,740,595

2 Sheets-Sheet 2 WATER COOLED ROTOR FOR DYNAMOELECTRIC MACHINESBACKGROUND OF THE INVENTION The present invention relates to the coolingof dynamoelectric machines, and more particularly to a liquid cooledrotor for machines of large size such as turbine generators.

Large turbine generators are. usually of the inner cooled, or directcooled, construction in which a coolant fluid is circulated through ductmeans in the stator and rotor slots in direct thermal relation with thecurrent-carrying conductors inside the ground insulation. This type ofconstruction provides a very effective cooling system and has made itpossible to greatly increase the maximum ratings obtainable in largegenerators without exceeding the permissible limits of physical size.The coolant used in these machines has usually been hydrogen which fillsthe gas-tight housing and is circulated by a blower on the rotor shaftthrough the ducts of the stator and rotor windings and through suitableducts in the stator core.

As the maximum ratings required in large generators have continued toincrease, it has become necessary to further improve the cooling ofthese machines in the largest sizes. A substantial improvement incooling can be obtained by the use of more efficient coolant fluids suchas liquids. This has been done in stators by circulating a liquidcoolant such as water through the ducts of the stator winding, and asubstantial improvement in cooling has thus been obtained. A substantialfurther improvement can be obtained by applying liquid cooling to therotor by circulating water or other suitable liquid through passages inthe rotor windings.

There are many problems involved in circulating a liquid coolant throughthe rotor of a large generator. One of the most difficult-problems isthat of introducing thewater into the rotor and discharging ittherefrom. This is preferably done as close to the axis as possiblewhere the pressure in the liquid is at its lowest value, and onesuitable construction for this purpose is shown in a copendingapplication of L. P. Curtis et al, Ser. No. 144,050, filed May 17, 1971,and assigned to the assignee of the present invention. In thisconstruction, the liquid is introduced through an annular passage in theaxial bore at one end of the rotor shaft and flows from this passagethrough radial passages to an annular distribution chamber on the rotorsurface from which it flows to the passages in the winding conductors.-At the discharge end of the rotor, the liquid flows from the conductorsto a similar chamber and through radial passages to the central bore ofthe rotor through which it flows to. the end of the shaft and isdischarged through radial passages with suitable sealing means.

Since the heated water flowing through the passages in the rotor can bequite corrosive, it is necessary to protect the steel of the rotor fromcorrosion. This is done inaccordance with the present invention byproviding liners for all passages through which the water flows. Theseliners may be made of any suitable corrosion resistant material but arepreferably made of stainless steel. When stainless steel liners are usedin this manner, the liners become heated from the heated water flowingthrough them and tend to expand more than the steel rotor, both becausethey are at a somewhat higher temperature and because they may have agreater coefficient of thermal expansion than the special alloy steel ofwhich the rotor is usually made. Excessive stresses and possible damagecan therefore result if provision is not made to permit thisdifferential thermal expansion of the liner. When a long tubular linersuch as is used in the bores of the rotor shaft is utilized, it ispossible in some instances to provide for thermal expansion of the linerby anchoring it at one end only and permitting it to move axiallyrelative to the shaft, as shown for example at the entrance end of therotor in the above mentioned Curtis et al application, and as proposedin Cuny et al US. Pat. No.

3,497,736. This solution of the problem, however, is-

not available where the liner must be attached at both ends to fixedpoints in the rotor. Thus, at the discharge end of the rotor, the waterflows through radial passages to the bore of the shaft and through thebore to a second set of radial passages near the end of the shaftthrough which it is discharged. The stainless steel liner in the shaftbore between the two sets of radial passages must be anchored to radialstainless steel tubes in the passages at both ends, and if the liner isof substantial length, as is the case in the very large generators forwhich the invention is intended, the differential thermal expansion willbe sufficient to stress the radial tubes beyond permissible limits.

SUMMARY OF THE INVENTION In accordance with the present invention,differential thermal expansion of a stainless steel liner in the shaftbore of a large rotor is provided for by means of a bellows deviceinserted in the liner to absorb the expansion of the liner. Conventionalbellows devices are not suitable for this purpose since they usuallyhave thin walls for flexibility, so that they are susceptible tocorrosion or erosion resulting in relatively short life, and usuallywould have essentially line contact between the outer periphery of thebellows convolutions and the rotor surface, which would cause excessivebearing pressure and would be undesirable. A bellows of special designis therefore utilized in the present invention having relatively thickdiaphragm portions with essentially cylindrical exterior surfaces forcontact with the shaft to minimize any tendency to corrosion or erosionand to reduce the contact pressure due to the centrifugal forces. Thebellows also includes provisions for preventing accumulation ofcorrosive debris in the bellows and for making it sufficiently rigidwhile maintaining sufficient flexibility to absorb the longitudinalexpansion of the stainless steel liner in which it is inserted.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fullyunderstood from the following detailed description of an illustrativeembodiment, taken in connection with the accompanying drawings, inwhich:

FIG. 1 is a view in longitudinal section, partly in elevation, of aturbine generator having a liquid cooled rotor embodying the invention;and

FIG. 2 is an enlarged fragmentary longitudinal sectional view of thedischarge end of the rotor shaft.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring first to FIG. 1 of thedrawings, the invention is shown embodied in a large turbine generatorof typical construction although it should be understood that the rotorof the present invention may be used in any desired type ofdynamoelectric machine.

As shown, the generator has a stator core supported by frame rings 12 ina substantially gas-tight outer housing 14. The stator core 10 is of theusual laminated construction, having a generally cylindrical boretherethrough, and the laminations are clamped between suitable endplates 15 in the usual manner. The stator core 10 has longitudinal slotsin its inner periphery for reception of a stator winding 16 which may beof any suitable type but which is shown as being a liquid cooledwinding. For this purpose circular inlet and discharge manifolds 17 areprovided at opposite ends of the machine and connected through suitablemeans, generally indicated at 18, to circulate a coolant liquid such aswater through the coils of the stator winding 16. The manifolds 17 maybe connected as indicated diagrammatically at 19 to an externalrecirculating system of any desired type. The construction of a liquidcooled stator suitable for use with the present invention is disclosedand claimed in a copending application of F. P. Fidei, Ser. No. 31,296,filed Apr. 23, 1970, and assigned to the assignee of the presentinvention, now U.S. Pat. No. 3,634,705, although other suitableconstructions might also be used. The housing 14 is filled with acoolant gas, preferably hydrogen, which is circulated throughtheinterior of the housing to cool the stator core by flow through theusual radial cooling ducts, and suitable baffling of any desired typemay be provided in the housing to direct the flow of gas therein.

The machine has a rotor member 20 which is disposed in the bore of thestator core 10 and supported in bearings 21 at the end of the housing14. The bearing assemblies preferably include gland seals to preventleakage of gas along the rotor shaft. The bearings and gland seals maybe of any suitable or usual construction and have not been illustratedin detail as they are not a part of the invention. The rotor 20 has acentral body portion 23 which is provided with peripheral slots in theusual manner for the reception of a rotor winding 24. The rotor winding24, which is the field winding of the generator, may be of anysuitabletype and is constituted of copper conductors which extend longitudinallythrough the slots of the rotor body and generally circumferentially inthe end turn portions which are visible in the drawing. The end turns ofthe rotor winding are supported against rotational forces by the usualheavy retaining rings 25. The winding conductors 24 are made hollow withcentral passages extending through them through which the coolant liquidflows from one end to the other through both the circumferential endturn portions and the straight longitudinal portions. Any suitable ordesired type of flow pattern may be utilized for the coolant flow, andany desired type ofelectrical circuit may be used.

The rotor 20 has shaft portions 28 extending axially from the bodyportion 23 at each end thereof and ineluding journal portionssupportedin the bearings 21. The shaft portions have an axial bore 29 extendingthercthrough-and, in accordance with the usual practlce, the borepreferably extends for the entire length of the rotor as shown. In theillustrated embodiment of the invention. axial electrical leads 30extend through the bore 29 at the left hand end of the rotor,- as viewedin the drawing, and are connected to the rotor winding by means ofradial leads 31. The coolant liquid, which is preferably water, isintroduced at this end of the rotor through an annular passage 32 whichsurrounds the leads 30 in the bore 29 and which is connected to anannular distribution chamber 33 by radial passages 34. The chamber 33extends circumferentially around the surface of the rotor shaft 28 andis connected by generally axial connectors 35 of any suitable type tothe conductors 24 of the rotor winding. The annular passage 32 may bemade of two concentric tubes of stainless steel or other suitablecorrosion resistant material, and thus serves the purpose of a corrosionresistant liner for the shaft bore 29. The tubes of which the annularpassage 32 is made are anchored at the inner end to tubular stainlesssteel liners in the radial passages 34. The tubes 32 are otherwise freeto expand axially in the bore 29 to provide for differential thermalexpansion as more fully explained in the above-mentioned Curtis et alapplication.

At the right hand end of the rotor, as seen in the drawing, which is thedischarge end, the water flows from the rotor winding conductors throughconnectors 36 to an annular chamber 37 extending circumferentiallyaround the surface of the rotor shaft 28. The connectors 35 and 36 atopposite ends of the winding 24 may be of similar construction and eachconnector includes an insulating section. The water in the chamber 37flows radially inward through radial passages 38 to the bore 29 of therotor shaft, and axially through the bore to another set of radialpassages 39 at or near the outward end of the rotor shaft, through whichit is discharged into a stationary annular chamber 40 extending aroundthe circumference of the shaft. The water is drained from the chamber 40as indicated at 41 for recirculation, any suitable type of sealing meansbeing provided to prevent escape of water. The radial passages 38 and 39are provided with tubular liners 42 of stainless steel and the bore 29is similarly lined with a tubular liner 43 of the same material.

It will be seen that at the discharge end of the rotor, the liner 43must be attached to each of the liners 42 of the radial passages 38 and39. Since the tubular liner 43 is thus anchored at both ends, anydifferential expansion of the liner 43 relative to the rotor shaft 28will result in extremely high stresses applied to the liners 42 and thejoints between the liners 42 and 43 or to the liner 43 itself. It isnecessary, therefore, to provide some means for absorbing thedifferential expansion to prevent the occurrence of these excessivestresses.

in accordance with the present invention, differential thermal expansionof the stainless steel liner 43 is absorbed by a bellows device 44interposed in the liner 43. As shown more particularly in FIG. 2, thebellows 44 is of special design and is interposed directly in the liner43 by welding the bellows in place as indicated at 45. The bellowsdevice 44 is shown in the drawing as consisting of two separatedsections with a solid section 46 of liner between them, but this is doneonly for convenience in manufacture and the bellows 44 could be a singlebellows of suitable length. The bellows device 44 is preferably anintegral member machined from a single piece of stainless steel tubingas shown in the drawing. Each section of the bellows consists of anumber of convolutions 47 comprising a series of relatively thin radialwall portions or diaphragms connected at their inner and outercircumferences to form a bellows. The diaphragms are proportioned tohave sufficient flexibility to allow them to flex so that the bellowscan expand and contract and thus permit axial expansion and contractionof the stainless steel liner in which it is inserted.

lt will be noted that the bellows 44 differs in important respects fromthe conventional types of metal bellows. The usual commerciallyavailable bellows has relatively thin walls to obtain the desiredflexibility. Such thin walls are particularly susceptible to corrosionby heated water flowing through the bellows and are also susceptible toerosion by metallic particles or corrosion debris carried in the waterwhich flows at a relatively high velocity. Such corrosion debris alsowould tend to collect in the convolutions of a conventional bellowsbecause of the relatively high centrifugal forces to which it issubjected in the rotor of a large generator. Furthermore, theconventional bellows has relatively sharp or narrow ridges on its outersurface so that it would have essentially line contact with the surfaceof the shaft bore, and the high centrifugal force would result inexcessive bearing pressures and possible failure of the bellows.

In accordance with the present invention, a bellows design is providedwhich eliminates the above mentioned problems of conventional bellows.It will be seen from FIG; 2 that since the bellows is machined asdescribed above from. a stainless steel tube, the outer surfaces 48 ofthe bellows convolutions are generally cylindrical and the diaphragm canbe made thick enough to resist corrosion but with sufficient flexibilityto per mit expansion and contraction of the bellows. The cylindricalsurfaces 48 engage the inner surface of the shaft bore 29 with contactsof substantial area so that no excessive bearing pressures occur evenunder the relatively high centrifugal'forces due to the high speed ofrotation of the rotor. A tubular member 49, preferably also of stainlesssteel, is provided on the inside of each section of the bellows 44. Eachtube 49 is welded to the bellows at one end 50.but not at the other endso that the bellows is free to expand and contract without constraint bythe tube 49. The tube 49 extends over the convolutions 47 and preventsthe possibility of any accumulation of corrosive debris in theconvolutions of the bellows since it prevents access to theconvolutions, and also assures that the water flowing through thebellows will flow smoothly and uniformly. A plurality of small holes 51may be provided through the tube 49 to flush any stagnant water whichmay tend to accumulate in'the convolutions of the bellows. The bellowsdevice 44 is inserted directly in the liner 43, as mentioned above, andthe radial liners42 of the radial passages 38 and 39 are welded directlyin the liner 43. The ends of the axial liner 43'are closed and sealed bysuitable plugs or partitions 53to prevent leakage of water from the blystainless steel, and its design is such that any reasonable amount ofthermal expansion of the liner can be absorbed by compression of thebellows without resulting in excessive stresses at any point. Aparticular em- .bodiment of the invention has been shown and describedfor the purpose of illustration, but it will be apparent that otherembodiments and equivalent constructions are possible and all suchmodifications and embodiments are within the scope of the invention.

We claim as our invention:

1. A rotor for a dynamoelectric machine having a body portion and shaftportions, windings on the body portion having passages'for circulationof a liquid coolant therethrough, a coolant distributing chamber on atleast one of the shaft portions, means for connecting the chamber tosaid winding passages, said one shaft portion having a central axialbore adapted for coolant flow therethrough, a radial passage connectingthe bore to said chamber, a liner of corrosion-resistant material insaid bore, and bellows means interposed in said liner to permit thermalexpansion of the liner, said bellows having a plurality of convolutionsof generally rectangular cross-section with cylindrical outer surfacesand including an internal tube attached to the bellows at one end andextending over the convolutions, said tube having a plurality of holestherethrough.

2. A rotor for a dynamoelectric machine having a body portion and shaftportions, windings on the body portion having passages for circulationof a liquid coolant therethrough, a coolant distributing chamber on atleast one of the shaft portions, means for connecting the chamber tosaidwinding passages, said one shaft portion having a central axial boreadapted for coolant flow therethrough, a radial passage connecting thebore to said chamber, a liner of corrosion-resistant material in saidbore, and bellows means interposed in said liner to permit thermalexpansion of the liner, a second radial passage spaced from thefirst-mentioned radial passage and connecting said bore to the surfaceof the rotor, and a corrosion-resistant liner in each radial passage,said last-mentioned liners being joined to said bore liner and saidbellows being interposed in the bore liner between the radial passages.

3. In a rotor member having an axial bore and a corrosion-resistantliner in said bore, a bellows interposed in the liner to permit thermalexpansion thereof, said bellows comprising a plurality of convolutionsof generally rectangular cross-section having cylindrical outer surfacesfor engagement with the surface of said bore, and the radial wallportions of said convolutions being adapted to flex to effect expansionand contraction of the bellows.

4. The structure defined in claim 3 in which the bellows has an internaltube attached thereto at one end and extending over the convolutions,said tube having a plurality of holes therethrough.

1. A rotor for a dynamoelectric machine having a body portion and shaftportions, windings on the body portion having passages for circulationof a liquid coolant therethrough, a coolant distributing chamber on atleast one of the shaft portions, means for connecting the chamber tosaid winding passages, said one shaft portion having a central axialbore adapted for coolant flow therethrough, a radial passage connectingthe bore to said chamber, a liner of corrosion-resistant material insaid bore, and bellows means interposed in said liner to permit thermalexpansion of the liner, said bellows having a plurality of convolutionsof generally rectangular cross-section with cylindrical outer surfacesand including an internal tube attached to the bellows at one end andextending over the convolutions, said tube having a plurality of holestherethrough.
 2. A rotor for a dynamoelectric machine having a bodyportion and shaft portions, windings on the body portion having passagesfor circulation of a liquid coolant therethrough, a coolant distributingchamber on at least one of the shaft portions, means for connecting thechamber to said winding passages, said one shaft portion having acentral axial bore adapted for coolant flow therethrough, a radialpassage connecting the bore to said chamber, a liner ofcorrosion-resistant material in said bore, and bellows means interposedin said liner to perMit thermal expansion of the liner, a second radialpassage spaced from the first-mentioned radial passage and connectingsaid bore to the surface of the rotor, and a corrosion-resistant linerin each radial passage, said last-mentioned liners being joined to saidbore liner and said bellows being interposed in the bore liner betweenthe radial passages.
 3. In a rotor member having an axial bore and acorrosion-resistant liner in said bore, a bellows interposed in theliner to permit thermal expansion thereof, said bellows comprising aplurality of convolutions of generally rectangular cross-section havingcylindrical outer surfaces for engagement with the surface of said bore,and the radial wall portions of said convolutions being adapted to flexto effect expansion and contraction of the bellows.
 4. The structuredefined in claim 3 in which the bellows has an internal tube attachedthereto at one end and extending over the convolutions, said tube havinga plurality of holes therethrough.